Sustainable toothbrush where one can continually replace the head of the toothbrush as and when the bristles wear out. Saves plastic and $$.
Install rain sensors in traffic lights. Staying red longer when it's raining, pedestrians would have more time to cross the streets.
Change all car´s horns to random electronic samples of orchestral instruments, so we could make contemporary music out of traffic chaos.
turning garbage into useful. http://migre.me/60AON
iPhone controlled glasses that mimic contents of iPhone. Private/Hands free. Earbud attachment and web cam for external "live surroundings".
Add two existing technologies. Write and draw directly on the surface of a table is better than on the surface of a tablet.